An epidemiologic survey of roller-skating injuries in Metroville, a city with a population of 100,000 (during the midpoint of the year), produced the following data for a particular year:
Number of skaters in Metroville during any given month
12,000
Roller-skating injuries in Metroville
600
Total number of residents injured from roller-skating
1,800
Total number of deaths from roller-skating
90
Total number of deaths from all causes
900
The cause-specific mortality rate from roller-skating was:
90/600 × 100,000
90/100,000 × 100,000
90/1,800 × 100,000
90/900 × 100,000